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January 2, 2013

What Is A River?

Hi, my name is Emerald Robinson, and in this “What Is” video, we’re going to try to determine what exactly defines a river.

A river is a natural stream of fresh water that has a current, and moves toward another body of water such as an ocean, lake, or another river. Rivers can be of different sizes, and local terms can cause the actual definition of a river to be vague: what one person calls a river another might term a brook, a rill, or a creek.

A river’s origin is called its “source.” Since rivers flow downhill, sources are usually high in the mountains where water comes from snowmelt, or an underground spring. A river flows between its sides, or “banks” in what’s called its “channel.” The channel increases in size as the river gains water from other smaller streams, or “tributaries.” A river’s journey ends when it meets a lake or the sea, at a point called its mouth.

Rivers play an enormous role in shaping the earth through erosion, creating geological formations such as canyons. Rivers create as well as destroy: a river’s mouth is often clogged by silt and dirt that’s been carried down the river’s path. This sometimes forms a land mass called a delta.

Although there’s a little disagreement among geographers, it’s generally accepted that the world’s longest river is Egypt’s Nile River, which stretches over four thousand miles from Lake Victoria in Central Africa to the Mediterranean Sea.

The biggest river, though, is unquestionably the Amazon River, located in South America. Although it’s not quite as long as the Nile, it carries almost twenty percent of the world’s fresh water in its bed as it flows from its source in the Andes Mountains of Peru to its mouth on the Atlantic Ocean.